Metal punch



1931- J. H. ABRAMSON ETAL I 1,317,223

METAL PUNCH Filed Jan 25, 1928 Patented Au 4, 1931 UNITED STATES EN OFFICE.

JOHN Hnnnnnr ABRAMSQN/AND, EDWIN o. swansoir, on .nooxronn, rnnmorsas SIGNORS TO GREENLEE BROS. 8c 00., OF ROCK FZORDpILLINOIS, A CORPORATION OF ILLINOIS mar. Poison.

Application m January 25, 1928. Serla11 i'o. 249,888.

This invention relates to metal punches generally, although certain features of the present tool have special reference to the adaptation thereof for. use by electricians inv the enlargement of knockout holes in outlet and switch boxes. I

The standard outlet box, as is generally known, is provided with knock-outs of one size, usually seven-eighths of an inch, and whenever it was desired to connect up a larger sized conduit with the box, the electrician was confronted with the problem of enlarging a knock-out hole to the desired size by one makeshift method or another.- For ex- The tool of our invention is designed to be inserted in the standard knock-out'hole and,

by a simple, easy and speedy wrench operation, to punch out a slug tolerably concentricwith the originabhole to provide a larger hole of the right size to take a larger sized conduit. The tool comprises essentially only three parts, namely, a bolt arranged to be passed through the knock-out hole and to receive a nut outside the box, a cylindrical punch placed on the-bolt preferabl within the box next to the headflof the b0 t, and a cylindrical die placed on the bolt preferably outside the box next tothe nut threaded on thebolt. When thetool isused with the punch disposed inside the box, it is possible to punch out a hole in the side wall immediatelyalongside the back wall or an adjoining side wall. A special feature consists in ,4 the provision of a rod on the head of the bolt arranged to serve as a. handle in the application of the' tool to the'box and, thereafter,

by coming into engagement with some nearby-partiof the box to serve to hold the bolt against turning, so that the operation of the tool is reduced simply to the use of a wrench applied to 'the nut on the bolt. Where the aforesaid handle cannot be brought into engagement with some part of the box, it is intended that a piece of conduit he slipped over the same for holding.-

An especially noteworthyfeature of the tool of our invention consists in the provision of a punch of a'special form, the use of which makes it practically as easy to punch out a slug of a larger diameter as one of a smaller diameter and to make a clean cut in either case. For this purpose We provide a pair of diametrically opposed protruding spurs or teeth on the punch'arranged to pierce through the wall of the box at the commencement of the punching operation and portions rearwardly inclined relative to said spurs to provide shear edges arranged thereafter to cooperate withthe die as the punch is drawn into the latter to cut out a perfectly round slug. Due to the special form of the punch, a decided advantage is derived in that the slug punched out is bent in the operation of the tool to a V-form, thus making the same smaller than the bore of the die so that it is comparatively easy to remove the same.

The invention is described in greater detail in the following specification'wherein refers (shoe is made to the accompanying drawings, in which Figure 1,-is a view of. an ordinary outlet box showin thetool of our invention mounted in one of t e knock-out holes preparatory to the punching outflof a slug to enlarge the same;

' Fig. 2 is anenlairged horizontal section. taken on the line 2-2 of Fig. 1,=and r Fig. 3 is an isolated perspective of the-novel form of punch which we prefer to'employin vour tool.

The samereference numerals are applied to, corresponding parts in the three views.

The box-shown at 5 may here arded as I any standard .outlet box to whic several conduits, such as that shown at 6, may ,be con nected and anchored, as by means of nuts I, The knock-out holes provlded in a standard box, one of which is shown at 8 inFi 52, are always one certain size totake onealf inch. conduit, as is generally known, these 3% holes being of seven-eighths of an inch diameter. The tool of our invention is provided for the purpose of punching out slu s of different diameters as ma be require for different sized conduits w erever it is necessary to connect up a larger sized conduit with the outlet box, or switch box, as the case may be. Accordingly, we rovide a tool comprising a bolt 9 of a size to be insertable freely through a knock-out hole. and provide a punch 10 and die 11 for each of the various standard sized conduits which an electrician is ever apt to have to deal with. In other words, the tool comprises essentially only three parts, the bolt, the punch, and the die, a complete set of punches with dies to match being provided for the different sizes of conduits and the bolt being arranged for use interchangeably with any punch and its companion die. The punch 10, as clearly appears in Fig. 3, is of cylindrical form with a central hole 12 for the reception of the bolt 9, the punch belng arranged to be placed on the. olt next to the head 13 thereof and preferably'within the box, for the reason that that makes it possible to work u close to the back wall or an adjoining si e wall. The punch is arranged to fit slidably in the cylindrical bore 14 of the die 11 disposed outside the box and having a central hole 15 to take the threaded end 16 of the bolt 9. The nut 17 threading on the bolt abuts against the back of the die and is arranged in the tightening thereof to draw the punch into the die. The bolt 1s held against turning by a rod 18 passed through a transverse hole 19 in the head 13 of the bolt, said rod being arrangedto bear against an adjoining side wall of the box, as shown n Fig. 1, or possibly against the back wali thereof, epending on where the tool is bemg used. The rod is slidable in its hole and has the ends thereof upset as at 20 gust enough to keep it from dropping out. I it should hapn that the tool is bemg used in such a place where the rod will not reach some part of the box in the manner just described, then it is contemplated that the electrician may slip the end of a piece of conduit over the rod to hold the same. The though is to reduce the operation of the tool merely to the use of a wrench applied to the nut 17. The nut is of a size such that the wrench which every electrician carries in his kit will fit the same.

No extra tools are therefore necessitated. Al-

though an ordinary nut is shown at 17, we contemplate the use of one having a ratchet built therein to make it handier to operate the tool in a relatively confined space. The imthe punch makes it practically as easy to punch out a large slug as a small one. The working faceof thepunch is provided with diametrically opposed protruding sharpened spurs or teeth 21 arranged to bite into and pierce through the wall first when the punch is drawn axially into the die. The spurs are provided with a vertically inclined wall 25 on the face 22 of the punch 10 to provide fiattened side portions 26 and 27 on eithersi'de of the. point 21, an inclined face 28 extending between the wall 25, the point 21 and the flatstruction permits shearing of the metal to proceed slowly until the spurs have passed through before the face 22 of the punch comes into contact therewith and results in a spur of substantial thickness of metal. Receding from the spurs 21 are rearwardly inclined portions 22-converging in-the form of a V diametrically of the face of the punch, as indicated at 23. The edges 24 of these portions of the face of the punch serve as shearing edges which, in cooperation with the die, serve to cut the wall of the box to remove a slug therefrom of truly circular form; an exact counterpart of the bore 14 of the die 11. It is due to this shearing action that the tool works so easily and that there is hardly any difference in the operation of the tool in punching out different sized slugs, inasmuch angle at 23 between the portions 22 being greater for smaller sized punches than for those of larger size. To state it differently: The face of a smaller punch is so conformed that the stroke of the punch from the start to the finish of the punching operation is shorter than in the case of a larger punch. A distinct advantage derived in theuse of a punch of the form justdescribed is that the slug punched out is bent into V-form, shown in dotted lines in Fig. 2, because of the fact that the'cutting out of the slug commences at diametrically opposite points and progresses circle-wise in both directions to the finish points, and as the wall is penetrated, the portions of the slug conform to the face of the punch, with the result that the slug eventually cut out is sufliciently smaller across one dimension thereof that it'comes out of the die readily, or at least a screw driver bit, or other pronged tool, may be inserted alongside the same to dislodge it. The contraction in 7 size of the knockout hole 8 caused by the bending of the slug is not sufficient to make the ug bind on the bolt, the bolt being provided nall enough with that in mind.

It is believed the foregoing description mveys a clear understanding of our invenon and of its various objects and advaniges. While we have referred to the advani-ges in the use of the tool by electricians for ie punching of holes in outlet boxes and witch boxes, it should be evidentthat the )01 might be employed to good advantage )1 other purposes. No limitation should ierefore be regarded as imposed on the aplication of our invention. Furthermore, all iodifications and adaptations are intended be covered in the appended claims.

'0 claim:

1. A metal punch comprising a punch elewill. and a die element having a bore to rerive the punch element, the working face of ie punch element having a. projecting spur t the peripheral edge thereof arranged to resent a sharp point and flat sides to the 'ork to pierce the work first as the punch lenient enters the die element, and said nneh element having substantially the rest t' the working face thereof inclined with repectto a normal to the direction of its moveient to provide, with said spurs, peripheral nearing edges to exert a shearing action fol- )wing the piercing of the work by said spur.

2. A metal punch comprising a cylindrical unch element, and a die element having a vlindrical bore for slidably receiving the unch element, the working face of the punch lenient being inclined rearwardly from two .ibstantially diametrically opposed points hereoi in converging relation to provide 'eripheral shearing edges when the punch lenient is drawn axially into the die element, projecting work-piercing and shearing spur t at least one of said diametrically opposed oints, said spur having a sharp point, fiatened side portions providing a portion of aid peripheral shearing edges, and an inlined face joining said point and said die IOItlODS. v

In witness whereof we hereto afiix our sigiatures. 7

JOHN HERBERT ABRAMSON.

EDWIN C. SvVANSON. 

